A two way mail envelope may be constructed with an extra closure flap folded forward from the back panel of a mailing envelope for being withdrawn and used to reseal the envelope when it is used as cover for reply mail, and serving as well to cover and obliterate from view cancelled postage. Customarily, such an envelope has either been provided with a flap large enough to cover the initial delivery address appearing on the front face of the envelope or has had the initial delivery address printed on a peelable tab which is removed from the face of the envelope for re-use of the envelope as reply mail cover. Universally, past practice has been to obliterate or remove an initial mail address from the face of an envelope used for reply mail.